2. The Centers for Disease Control and Prevention categories of body mass index (BMI) are normal (18.5-24.9 kg/m2), overweight (25-29.9 kg/m2), class I obesity (30-34.9 kg/m2), class II obesity (35-39.9 kg/m2), and class III obesity (>40 kg/m2). In the United States, 72.3% of men and 64.1% of women are overweight or obese. Among children, 16.9% are obese. Higher rates of obesity are observed among non-Hispanic black and Hispanic women. Rates of obesity are highest in the South, eastern Appalachia, and costal North and South Carolina. Colorado has the lowest rate of obesity.

3. BMI is not always the best measure to discriminate risk of disease associated with adiposity. BMI has a pooled sensitivity of 50% and a pooled specificity of 90% to identify excess adiposity. Waist circumference is a simple method to assess for central obesity, which has excellent correlation with abdominal imaging. Sagittal abdominal diameter may be a better marker of abdominal visceral adiposity than waist-to-hip ratio, but has not been well validated.
4. Other measures include ratio of waist to hip. Computed tomography (CT) scans can measure adiposity including visceral adiposity accurately, but are not routinely used in clinical practice. Imaging modalities including CT scans, magnetic resonance imaging (MRI), and proton MR spectroscopy can differentiate differences in liver fat content. Liver fat content may be more related to diabetes mellitus and high triglycerides than measures of visceral adiposity and, thus, may identify individuals at greater risk for cardiovascular disease and/or diabetes mellitus.
5. Visceral adiposity is associated with increased risk of chronic diseases, including cardiovascular disease. Factors associated with visceral adiposity include increasing age, male sex, menopause, smoking, high caloric diets, and sedentary behaviors. Blacks are more prone to subcutaneous fats, whereas Asians are more prone to visceral fat deposits.
6. Assessing body composition can be done with several methods. Anthropometric measures such as limb circumference and skinfold thickness are low cost, but can underestimate body fat. Near infrared interaction has been used to measure body fat, but has been observed to have limited accuracy compared to other measures. Additional measures include hydrostatic weighing, plethysmography, dual-energy X-ray, and absorptionmetry.
7. CT scans and MRI are now considered the gold standard for measurement of fat distribution.
8. Measurement of ectopic fat or fat deposits in the liver, skeletal muscle, and cardiac muscle is associated with cardiometabolic risk factors. Proton MR spectroscopy can reliably measure such ectopic fat deposits.
9. Changes in fat mass can be assessed through repeated measures, including BMI and waist circumference. Changes in waist circumference have been observed to correlate with changes in cardiometabolic risk factors. To date, no long-term studies have assessed the relationship of changes in body fat composition and clinical outcomes.

10. Currently, BMI and waist circumference are the primary tools to assess for adiposity. For all patients, counseling regarding healthy dietary and activity behaviors is recommended. Among patients with increased BMI or high waist circumference, assessment of other cardiometabolic risk factors is recommended.